Riesite
A dense form of titanium dioxide made from rutile by the shock of an asteroid impact.
Key facts
- Formula
- TiO2
- Family
- High-pressure minerals
- Crystal system
- Monoclinic
- First described
- the Ries impact crater, Germany, 2020
Riesite was described in 2020 from shocked rocks of the Ries crater in southern Germany, made by an asteroid impact about 15 million years ago, and is named after the crater. It has since been reported from the Suizhou meteorite.
What it is
Riesite is a high-pressure form of titanium dioxide, more densely packed than rutile. In the laboratory, rutile changes first to a form with the α-lead oxide structure and then to denser forms as pressure rises; riesite is a natural record of these changes, preserved because the shock passed so quickly.
Where it is found
It occurs in rutile grains in shocked rocks from the Ries crater, together with other dense forms of titanium dioxide. Similar shock forms of titanium dioxide occur in other craters and in shocked meteorites.
How it is recognised
It is identified by electron diffraction and Raman spectroscopy within shocked rutile grains.
Did you know?
The town of Nördlingen sits inside the Ries crater, and its church is built of impact-shocked rock.
Coesite, found at the Ries in 1961, helped prove that the crater was made by an impact.